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How James Paxton became the Yankees’ top offseason target

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An unassuming fourth-round pick showed promise before an analytical change made him a star.

James Paxton was a key offseason acquisition for the Yankees. Photo by Elsa/Getty Images

Spring training is in full swing, almost all of the major free agents have signed, and we can now turn our attention to action on the field instead of off it. The top winter maneuver on the Yankees’ part was trading top pitching prospect Justus Sheffield for James Paxton, whose s on-field work I want to delve into today.

I’ve followed Paxton for a long time, mostly because of his nationality. There are few enough Canadians in the majors that I like to keep tabs on them all, and he is no exception. It’s been interesting then to monitor the two separate narratives that have dominated his career.

First, he was regarded as a player with ample potential, but one who hadn’t put it together consistently at the major-league level. He didn’t strike out guys at an elite level but showed quality offerings, he walked a few too many men, that kind of thing. Pretty typical stuff for developing pitchers. Something clicked in Paxton a couple of seasons ago, however, and the narrative went from untapped potential to a legitimate Cy Young candidate who needed to avoid injury.

What clicked? Location, location, location.

In a way, Paxton’s emergence as a stud starter stems from directly responding to the launch angle revolution. As hitters have prioritized uppercut swings to get the ball in the air, Big Maple has prioritized pitches up in the zone, especially his four-seam and cut fastballs, which he throws a combined 80% of the time or so:

Here’s his heat map from 2016, his first real quality season in MLB by both ERA and FIP. His strikeouts weren’t quite what we see from him today, but he was good enough that the “untapped potential” narrative started to fade.

Now look at how his pitch location changed over two years:

You can see how he’s demonstrably moved his fastballs up in the zone. That entire bottom row of the strike zone has been abandoned, and the second bottom row has seen a shift as well. Meanwhile, he’s brought the heat up closer to the letters and top of the zone.

This trend even holds on two strikes, the situation where you see most pitchers move out of the zone:

The lower left quadrant is still Paxton’s favorite target for put-away pitches, but he works up in the zone and over the plate an awful lot.

Funnily enough, this two-strike approach is almost identical - albeit mirrored - to another top-flight strikeout pitcher, Luis Severino:

This indicates that the Yankees aren’t likely to mess with Paxton’s approach and usage too much, since they’ve allowed Severino to go after hitters in pretty much the same way.

So we know what Paxton has done differently, and now the question is why.

The answer ties into the launch angle revolution. Statcast, wearable tech, and the rest have allowed teams to plot swing planes and pitch trajectories. They can project, within a range, the most probable outcomes for a given pitch against a given player’s swing. As hitters have moved to uppercut swings, it’s become more and more advantageous for pitchers to pitch up in the zone and keep the ball above the swing planes of most hitters.

Although this goes against conventional wisdom, hitters increasingly struggle against pitches up in the zone because their swings all pass through the bottom of the zone. When you combine that trend with the fact that Paxton throws 98 mph, you can see why he’s able to generate so many strikeouts.

As a very interesting and possibly meaningless tidbit, one of the big benefits J.D. Martinez supposedly brought to the Red Sox was an increased focus on swing planes, encouraging players to hit the ball in the air more. Martinez does that effectively, of course, but Mookie Betts’ average launch angle rose four degrees in 2018. Jackie Bradley Jr.’s launch angle went up three degrees. Xander Bogaerts’ rose four and a half degrees. Maybe that’s nothing, but it sure looks like the Martinez Approach really did rub off on the Red Sox.

That could potentially make Paxton even more valuable, as this trend of working up in the zone counteracts the Boston’s apparent belief in dropping the swing and lofting the ball. It’s possible Paxton is the perfect antidote to Boston’s philosophy, or is at least a better tonic than someone like CC Sabathia. The team’s elder statesman actively and openly works down in the zone to induce soft contact, but whose pitches now perfectly square up with Red Sox swing planes.

James Paxton is an analytical success story, and the fact that he was so open to making a significant change for a team like the Mariners is really good news, since the Yankees are more advanced and forward-thinking than just about any other team in baseball. He seems like the perfect acquisition for New York, and is poised to become as big a star as there is among starting pitchers.